1. Field of the Invention
The present invention relates to a core-sheath type composite filament having superior functionalities (e.g., deodorizing properties, antimicrobial properties), spinning properties, stretching properties, physical properties (e.g., strength, dimensional stability), and economy (i.e., cost), which is useful for various applications including filters of air conditioners or air cleaners, and to a process for the production of the same. Also, the invention relates to a heat fused article obtainable from such a composite filament.
2. Description of the Conventional Art
As filters to be incorporated into air conditioners or air cleaners, filters made of a polypropylene filament that is not only advantageous from the standpoint of production cost but also superior in characteristics such as moldability, mechanical strength, water resistance, and chemical resistance, are widely used.
It is also known that polypropylene for a filter is incorporated with a synthetic bactericide or carried with a catechin as a tea-extraction component, through external attachment or internal addition.
For example, Japanese Patent Laid-Open No. 99656/1989 mentions an antibacterial electret filter comprising polypropylene fibers having 0.1% or more of a bactericide incorporated therein. However, the bactericide that is used in the examples of this patent publication is thiabendazole as a synthetic bactericide.
Further, Japanese Patent Laid-Open No. 148407/1995 describes an antiviral filter comprising a filter impregnated with, or a filter material incorporated with, a virus-inactivating agent comprising, as an active ingredient, a tea-extraction component. The tea-extraction component as referred to herein means a tea polyphenol such as a catechin. In the examples of this patent publication are given (A) an example in which the tea-extraction component is dissolved in water to prepare an aqueous solution, which is then impregnated and attached to an electret filter; and (B) an example in which polypropylene is mixed with the tea-extraction component, and the mixture is molten to form a film, which is then cut and fabricated into a non-woven fabric.
Moreover, Japanese Patent Laid-Open No. 266828/1996 describes an antiviral filter comprising a dust-collecting filter and a filter impregnated with a tea-extraction component. The tea-extraction component as referred to herein means a tea polyphenol such as a catechin. Further, the filer impregnated with a tea-extraction component as referred to herein means an electret filter, an HEPA filter, a high-performance filer, a middle-performance filter, a bag filter, etc.
In addition, Japanese Patent Publication No. 3969/1988 (Japanese Patent No. 1,456,233) owned by one of the present applicants describes a composite monofilament comprising high-melting polypropylene as a core component and a low-melting polyolefin as a sheath component. This patent publication also mentions that this monofilament is fabricated into a net-like state. However, this patent publication does not describe that the monofilament is carried with an active ingredient such as a bactericide. In this monofilament, since not only a necessary strength is obtained by the core component, but also heat fusion properties are obtained by the sheath component, it is easy to fabricate it into a net-like state or a non-woven fabric-like state.
In the case where the tea-extraction component is dissolved in water to prepare an aqueous solution, which is then externally impregnated and carried in a filter, namely, in the attachment and carrying method by impregnation, the tea-extraction component is compatible with water, and hence, fixing properties and waterproof properties are not sufficient. Therefore, when this filter is used upon being brought into contact with water, or is used while often washing with water, it involves such a defect that the tea-extraction component as an attaching component is readily lost.
In the method in which the tea-extraction component such as a catechin is internally added to (i.e., incorporated into) polypropylene as a filter material and then melt formed, since the tea-extraction component such as a catechin, which is originally soluble in water, is incompatible with polypropylene as a non-polar resin, it likely bleeds out onto the filament surface to generate stains. Further, when the filament is dipped in water or washed with water, a major part of the extraction component elutes out, whereby the effect is drastically reduced. Even when the internal addition amount is increased taking into consideration of the bleeding-out, the elution amount is still high during contact with water. Accordingly, it is inevitable that not only the production cost is high, but also the spinning properties, stretching properties and strength are reduced. In addition, in this internal addition method, during the melt forming, a considerable amount of an effective part of the tea-extraction component is volatilized out, and hence, it is inevitable that the relatively expensive active ingredient is lost.
Under such circumstances, the present invention is aimed to provide a core-sheath type composite filament, in which a functional component is hardly lost due to volatilization during the melt forming; bleeding of the internally added functional component is effectively inhibited; the internally added functional component does not adversely affect spinning properties, stretching properties, and physical properties (e.g., strength, dimensional stability); the internal addition amount of the functional component can be greatly reduced, leading to an advantage from the standpoint of production cost; superior functionalities (e.g., deodorizing properties, antimicrobial properties), which the functional component inherently possesses, can be exhibited to a maximum extent; even when used upon contact with water, the composite filament is durable so that the functionalities can be kept over a long period of time; and even when used upon contact with a human body, the composite filament is high in safety. The present invention is also aimed to provide a process for the production of the core-sheath type composite filament as well as a heat fused article obtained from the composite filament.
Specifically, the composite filament according to the present invention is a core-sheath type composite filament comprising a core component X and a sheath component Y, wherein the core component X is formed from a first polyolefin resin (H), and the sheath component Y is formed from a second polyolefin resin (L) compounded with at least one functional component (A) selected from the group consisting of a catechin, a saponin, a tea-leaf powder, a tea-leaf extract, and tannin (tannic acid), and a ceramics component (C).
The process for the production of the composite filter according to the present invention comprises co-extrusion forming a first polyolefin resin (H) and a second polyolefin resin (L) compounded with at least one functional component (A) selected from the group consisting of a catechin, a saponin, a tea-leaf powder, a tea-leaf extract, and tannin (tannic acid), and a ceramics component (C) at a temperature higher than melting temperatures of the respective components, such that the first polyolefin resin (H) becomes a core component X and that the second polyolefin resin (L) compounded with the functional component (A) and the ceramics component (C) becomes a sheath component Y, thereby obtaining a core-sheath type composite filter constructed of the core component X and the sheath component Y.
The heat fused article in a net-like state according to the present invention is comprised of a heat fused material of a textile made of the above-described composite filament. Further, the heat fused article in a non-woven fabric state according to the present invention is comprised of a heat fused material of the above-described composite filament.